Insomnia is common among older adults with sleep continuity disturbance being nearly three times more common in the elderly than in the overall population. This increased prevalence is of significant clinical concern as insomnia represents, in the population at large, a risk factor for new onset and recurrent psychiatric and medical illness. For older adults, the increased prevalence of insomnia may serve to make them more vulnerable to the illnesses that occur with advancing age. Despite this, very little is known about the natural history of insomnia and still less is known about the factors that appear to uniquely predispose, precipitate, and/or perpetuate insomnia in the elderly. The lack of work within this area has left the field without incidence data and temporal trends regarding new onset acute and chronic insomnia in general and in specific in older adults. Furthermore, there is no empirically based assessment of the factors that are thought to moderate/mediate maintenance of good sleep, the occurrence of (and remission/recovery from) acute insomnia, and the transition from acute to chronic insomnia. In the absence of such data, it has been hypothesized that acute insomnia occurs as an interaction between predispositional factors and acute stress (perceived or real threat) and that chronic insomnia occurs as a result of cognitive, behavioral, and conditioning factors. None of these sets of factors have ever been assessed prospectively, assessed for their relative contribution to clinical course, or assessed for how they vary with age. Accordingly, we propose to conduct a large scale, longitudinal, internet-based study across three age cohorts (middle aged [35 to 55 years], Young Elders [55 to 75 years], and Older Elders [75 years and older]). Each age cohort (comprised of 500 good sleepers and 500 individuals with acute insomnia) will be recruited via an international polling agency and surveyed on seven occasions (original Zogby survey, Intake, one, three, six, nine and 12 months) regarding life events, sleep continuity, health, mental health status, and other factors that have been theorized to mediate clinical course. In addition to the longitudinal self-report assessment, a sample of 90 subjects (over three years) with acute insomnia will be recruited from the parent sample (local to the Philadelphia region) to take part in two lab-based studies (once when the insomnia is acute and then again when the subject exhibits remission or chronic insomnia). The lab assessment will include two nights of polysomnography, the collection of urine samples at each void (to assess cortisol and melatonin levels), and the administration of an attention bias test regimen. The primary aims of the study are to: 1) profile the incidence rates of acute and chronic insomnia across the three age cohorts; 2) assess which of the theory driven factors best accounts for (alone and in combination) the various clinical course scenarios; and 3) determine if lab based biological measures distinguish between the various clinical course scenarios